


Marcuck

by Ulysseus



Category: Star vs. The Forces Of Evil
Genre: Cuckolding, Dick Girl, Domination, F/F, F/M, Harem, Humiliation, Incest, Moral Degradation, Other, Pseudo-Incest, Sibling Incest, Small Penis, ntr, small penis humiliation
Language: English
Status: Completed
Published: 2020-09-18
Updated: 2020-09-18
Packaged: 2021-03-07 20:40:18
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,159
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26523835
Author URL: https://archiveofourown.org/users/Ulysseus/pseuds/Ulysseus
Summary: Marco has the girl of his dreams, the life he always wanted, what could possibly go wrong? Nothing, so long as his sister doesn't find out about his embarrassing secret and uses it to flaunt and humiliate him for her own fun.
Relationships: Marco Diaz/Jackie Lynn Thomas, Marco Diaz/Kelly, Marco Diaz/Mariposa Diaz, Mariposa Diaz/Jackie Lynn Thomas, Mariposa Diaz/Kelly, Mariposa Diaz/Star Butterfly
Kudos: 11





	Marcuck

**Author's Note:**

> Maybe this project won't be abandoned like all the others, we'll see!  
> Set in an AU where Mari is just a couple years younger than Marco, so basically imagine her as she appears in the Neverzone. Angie and Raphael are separated because I'm lazy and don't want to involve him.  
> Hope y'all enjoy, there's not much to this chapter, but I just wanted to get something out, I may be the world's least productive writer, but that doesn't mean I have to like it.  
> A billion ideas for this fic, let's hope I can at least get a few of them in

“Ugh, just forget it!” Mariposa Diaz shouted as she stomped up to her room, leaving her brother standing at the bottom of the stairs, concerned in the aftermath of their, rather confusing, argument.  
Marco wasn’t quite sure what Mari’s point had been, as she seemed to have been almost deliberately dodging her own question to him, leaving him unable to actually give any meaningful advice to his sister beyond the most generic points imaginable. Though their last few months had been somewhat strained, this was the first time Mari had exploded at him like that to him. The brother knew better than to pressure her though, he had already been briefed by his mom about what was going on: puberty. He knew about the stereotype about girls becoming hysterical and inconsistent when their time to mature came, but he never figured it would apply to his own sister like this. She always adored him when they grew up, he felt good knowing that she considered him her icon, which made their more recent interactions all the more distressing and confusing for him. In recent times, she had been more opinionated, stubborn, and confrontational about seemingly minor things going on around the house.  
Marco simply had to reassure himself that this was just a moody phase that she would have to work through, before she became the ever adoring little sister he had always known.

It was past midnight when Mariposa woke up, an overfull bladder refusing to sit through the night as the culprit for her rude awakening. Thankfully, the bathroom was just down the hall and years of practice stealing midnight snacks allowed the girl to glide down the hall without making a sound and reach the door in record time and quickly swinging it open.  
“Hey! Occupied!” Marco cried from inside, the bright light Mari instinctively flicked on illuminating the scene before her; her brother sitting with his pants down on the toilet.  
“Oh-ew, gross!” Mari cried, throwing a hand over her eyes in a vain attempt to wipe the scene from her mind.  
“Why didn’t you knock first?” Marco shouted, awkwardly standing up and trying to pull up his pants, one hand over his crotch as he struggled to keep his balance.  
“Why are you pooing with the lights off?” She asked, lowering her arm to take a look at the slightly less shocking scene, though still awkward, with Marco still unable to get his pants around his waist while spending a hand on keeping his modesty.  
“I wasn’t!” Marco said, defensively, “I was just taking a leak”  
“What? Then why were you sitting down?”  
“Well, it’s so- look, you wouldn’t understand, it’s a guy thing” Marco said, defensively.  
“Hey, I’ve seen movies, I know guys always stand to pee,” Mari retorted, unconsciously stepping further into the room, towards her big brother.  
“Alright, I don’t really want to talk about this, okay?”  
“What the heck are you talking about? What’s the big deal?”  
“Because it’s weird!” Marco responded, before stopping to collect himself, seemingly given up on successfully pulling up his pants for the moment. “It’s not a big deal, I just like to sit so I don’t get my underwear wet.”  
“What? What are you talking about? It shoots in an arc, how could you-?”  
“Not like that! I mean at the end, when it dries up, it kinda… dribbles in if I stand and pee…”  
“Wait, but your junk hangs out past your underwear, right? So shouldn’t that just fall into the toilet?” Mariposa asked, her suspicions beginning to grow as she took another step towards Marco.  
“Well…” Marco trailed off as a blush filled his face. “It’s just-”  
Before the boy could stammer out his next response, Mari’s impatience got the better of her as she quickly resolved herself for the action ahead; she quickly took another step forward and snagged Marco’s hands away from their job protecting his decency, shocking the Latino.  
But, more shocked than him was the Latina, whose impatient action brought a revelation she never expected in her wildest dreams. What was hidden behind his hands was… surprisingly little. Literally, she realized as she looked upon her own brother’s penis. While, obviously, not hard Mariposa was still taken aback by the sight, confused at what she was even seeing before the anatomy began to fall into place for her. His penis definitely wasn’t missing any vital parts, she saw, they were all just, so small. The tip couldn’t have been a full inch away from his pelvis, half of that distance made up by his head, what little shaft there he had was little more than a couple of wrinkles. Tucked behind it all was his sack, a tight little pouch that she couldn’t believe held a pair of testes, since it seemed to be smaller than a golf ball to her. Unfortunately for him, Marco’s smooth crotch left little room for concealment of the whole picture from Mari, leaving the whole scene to sink into her mind, along with a wicked idea.  
“Oh, I get it now, just assumed you were really cramming your junk behind your hands there, didn’t think it’d actually fit!” She laughed as Marco’s blush overwhelmed him and his shame gave him the burst of momentum needed to wrestle free of her grip and recover his exposed secret.  
“Mari! What the hell?” He shouted, shocked at the brazen move by his otherwise passive sister.  
“Please, not like there’s much to hide there,” She replied, snarkily.  
“Well, how would you even know? You’re not even 13 yet,” He shot back, crossing his legs to try and help cover his crotch even more.  
“Right, guess you wouldn’t have remembered from bath time together; welp, stand back “big bro”, you’re gonna need to for this,” Mari said with more swagger and confidence than she ever had before while her fingers began to pull at the waist of her pajamas, “Here’s what real hardware looks like.”  
With one sudden jerking motion, her pants were pulled down to near her knees, fully necessary to show off what she had to show her brother. While any surface inspection of Mariposa Diaz would appear to be a totally normal girl, she’s had a secret kept locked away from prying eyes since the day she was born; while female in every other department, a fluke, or perhaps a miracle, of genetics endowed the latina with a full set of male genitals in lue of a standard vagina. Beyond that though, it was apparent that she was also gifted with more than just the average penis, which she became aware of as puberty took hold of her in the previous months.  
Lying before Marco’s now shamefully hard penis, sat his sister’s, half erect and beginning to bounce and throb to life before him, but still already cleanly double his own length.  
“So… You think this bad girl here can reach past my pants, or should I take a seat whenever I need to tinkle?” She sneered at him as she began to idly run her hand along her swelling shaft, accenting the veins that pushed their way out from her length, a sharp contrast to her brother’s sleek member.  
“M-Mari, what the hell are you doing?” He cried out, barely believing the brash actions of his younger sister.  
“Aww, what’s the matter? Feeling a bit embarrassed seeing your sister in the nude? Or… could it be that you’re more embarrassed about how we compare downstairs?” She asked, closing the gap between her and her underdeveloped brother, to the point where their other heads were nearly touching.  
“I gotta admit, it is kinda pitiful; I mean, I’m supposed to be your baby sister, but here you are looking like an actual baby where it really counts!”  
“That’s enough! I-” Marco definitely had more to say, but Mari had other plans as she swung her still partially flaccid cock across, flicking his tip as the two met, pulling a mixture of a yipe and moan from the latino boy.  
“Hoooly shit! Did you just get off to that?” Mari asked in stunned disbelief, “I was just fucking around with that, but you really got something serious from that, didn’t you? Ha! No wonder I’ve never heard you getting to home base with Jackie in your room, you literally don’t have what it takes to close the deal, I didn’t get why a girl like “that” hadn’t already jumped your bones, but I bet it’s you that’s delaying it so she doesn’t find out about your little problem,”  
Marco wanted to respond, he wanted to tell Mari that she was acting totally inappropriately, that she stepped out of line, most of all though, he wanted to tell her that he had made it to second base with Jackie just two weeks ago and that they had agreed to pace things out, she certainly wasn’t as loose as she could sometimes look. But he didn’t. He was too scared to even open his mouth, because of the danger that Mari might touch him down there again and he might not be able to contain himself. So he stood there, a crystal clear pearl of pre budding on his tip as he looked down at his own sister’s hard cock.  
And there it stood, right in front of his, making him want to scream, want to cover up and run away and pretend this whole thing never happened. But he couldn’t, because there it was; sticking outwards like a pole, bouncing gently in tune with her heartbeat as the gap between his member and hers only seemed to grow more and more. While Marco had been too ashamed to measure his length in some time, knowing he wasn’t quite matching up to his peers, his last check put him at, roughly, two and a half inches, and he knew he hadn’t grown much at all since then. His sister’s on the other hand, must have been pushing past nine solid inches, with a girth to match, easy four times as thick around as his; leaving him standing 5 inches taller than her, and less than a tenth of her size. If it was simply a matter of size, it would be bad enough for the latino, but the differences did not end there. While his penis certainly stood taller than hers, it took him only a moment to realize that his steeper angle clearly came from the apparent weight difference in their respective shafts; his light hardware close enough to his body and not dragged down by gravity and its own mass to stand up straight while hers had to strain just to keep straight. Lower down, Marco was shocked at her scrotum, though Mari’s cock obscured most of the view, it certainly hung much lower than his own, which always seemed to keep so close to his body. He guessed that it must have been nearly the size of his fist and couldn’t help but wonder how he never heard it slapping against her thigh when she walked just about anywhere.  
“Got a good enough picture of it?” Mari asked, snapping him out of the trance he seemed to have fallen into, “If not, I’ll give you the cliff notes; you don’t match up and it’s honestly pathetic. Now, if you’d excuse me, I’ve got some business to attend to,” She said as she walked past him, giving his bare ass a quick smack as she made her way to the toilet, pulling a tense cry from Marco, who was just grateful she wasn’t looking as he let out a bit more of his pre from the contact, which fell onto the floor from him jumping in surprise.  
“See you tomorrow, baby brother,” Mari said as he shuffled out of the bathroom, making sure to emphasize the new title she had dubbed him with before he was gone.

Marco lied in bed, utterly confused, totally heart wrenched, and undeniably horny. Though he wanted to blot the whole scenario from his mind, the image of her sister, standing exposed in front of him refused to leave his head as he tossed and turned on his bed, before he finally gave in. Placing his thumb on the front and placing his two front fingers on the back, he got to work. Though his teeth were gritted as he started, it only took a few of his tugs before he fell into his pattern, cumming quicker than usual from the previous sensations as he let out his usual whimper as a trail of his clear semen leaked out after about twenty seconds.  
Exhausted from the ordeal, Marco did his best to get some sleep, his busy schedule for the week would need him at his best, as he prepared to turn the whole house into a romantic getaway for Jackie and himself to celebrate the beginning of summer vacation together.


End file.
